The process of this invention concerns the production of ethylene glycol from formaldehyde and a synthesis gas comprising carbon monoxide and hydrogen. More particularly, this invention provides a multiple-step process for producing ethylene glycol. The principal steps involve (1) production of glycolic and diglycolic acids and simultaneous separation of carbon monoxide and hydrogen in synthesis gas, (2) esterification of the acid product, and (3) reduction of the esters. In addition to the integrated reaction steps, the process utilizes specific recycling steps to enhance the efficiency of the esterification and hydrogenation reactions.
Commonly assigned U.S. Pat. No. 3,911,003 granted Oct. 7, 1975 describes an improved process for producing glycolic acid and diglycolic acid from formaldehyde and carbon monoxide employing a hydrogen fluoride catalyst. According to the disclosure, in cases where the glycolic acid product is intended as a feedstock in the production of ethylene glycol, the acid is esterified with methanol and then catalytically hydrogenated to produce ethylene glycol. While the chemistry of this procedure is satisfactory, it has been found that the economics of the process presents a problem for large scale commercial exploitation. The substantial cost of methanol esterification and hydrogenation is not entirely offset by the improved yields and reaction rates obtained through the use of a hydrogen fluoride catalyst.
Accordingly, it remains desirable to provide an effective process for preparing ethylene glycol from formaldehyde and a synthesis gas comprising carbon monoxide and hydrogen.